1. Field of the Invention
This invention relates to a semiconductor laser, its manufacturing method, semiconductor device and its manufacturing method, especially suitable for use in a ridge xe2x80x94structured semiconductor laser using nitride III-compound semiconductors.
2. Description of the Related Art
Vigorous researches and developments have been made in recent years about semiconductor lasers using nitride III-V compound semiconductors like A1GaInN as being semiconductor lasers capable of emitting light over the blue to ultraviolet regions necessary for realization of higher density of optical discs. In order to realize write type optical discs. optical power at least not less than 20 mW is required. A group of Nakamura et al. reported about fabrication of a high power laser using these kinds of material (Appl. Phys. Lett., 72(1998) 2014, Jpn. J. Appl. Phys., 37(1998)L627). This semiconductor laser has a ridge-shaped stripe, side surfaces of the ridge are protected by an insulating film such as SiO2, and its p-side electrode is configured to contact only the part of a p-type contact layer on the top surface of the ridge.
The reported semiconductor laser has practical problems, namely, exhibiting kinks in its optical output-electric current property and an increase of the current immediately after the power supply. Kinks demonstrate that higher mode oscillation occurs along with an increase of the optical output. To suppress it, it is necessary to decrease the. difference in refractive index between the ridge portion and the portion outside the ridge or reduce the stripe width. In this case, however, the portion outside the ridge is SiO2 or air having a small refractive index. Therefore, it is not easy to change the difference of refractive indices. Reducing the stripe width is attended with difficulties in the process.
On the other hand, the increase of the current immediately after the power supply is considered to be induced by thermal deterioration of the active layer. To prevent it, it is necessary to effectively discharge the heat generated in the active layer. In this structure of the semiconductor laser, however, since the portion of the ridge top surface other than the p-type contact layer surface is covered by SiO2 having a low heat conductivity, it is difficult to dissipate the heat.
It is therefore an object of the invention to provide a semiconductor laser capable of suppressing higher mode oscillation during high power output by stably controlling transverse modes and excellent in heat dissipation property, and a manufacturing method thereof.
Another object of the invention is to provide a semiconductor device excellent in heat dissipation property and having a long lifetime, and a manufacturing method thereof.
According to the first aspect of the invention, there is provided a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising:
a buried layer made of A1xGa1-xAs (0xe2x89xa6xc3x971) to bury opposite sides of the ridge-shaped stripe.
According to the second aspect of the invention, there is provided a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising:
a buried layer made of (A1xGa1-x)yIn1-xP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury opposite sides of the ridge-shaped stripe.
According to the third aspect of the invention, there is provided a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising:
a buried layer made of ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury opposite sides of the ridge-shaped
According to the fourth aspect of the invention, there is provided a method for manufacturing a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising the steps of:
making the ridge-shaped stripe; and
growing a buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61) to bury opposite sides of the ridge-shaped stripe.
According to the fifth aspect of the invention, there is provided a method for manufacturing a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising the steps of:
making the ridge-shaped stripe; and
growing a buried semiconductor layer made of (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury opposite sides of the ridge-shaped stripe.
According to the sixth aspect of the invention, there is provided a method for manufacturing a semiconductor laser having a ridge-shaped stripe and made by using nitride III-V compound semiconductors, comprising the steps of:
making the ridge-shaped stripe; and
growing a buried semiconductor layer made of ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury opposite sides of the ridge-shaped stripe.
According to the seventh aspect of the invention, there is provided a semiconductor device having a projection on a nitride III-V compound semiconductor base body, comprising:
a buried semiconductor layer made of A1x Ga1-xAs (0xe2x89xa6xc3x97xe2x89xa61) to bury a portion around the projection.
According to the eighth aspect of the invention, there is provided a semiconductor device having a projection on a nitride III-V compound semiconductor base body, comprising:
a buried semiconductor layer made of (A1x Ga1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury a portion around the projection.
According to the ninth aspect of the invention, there is provided a semiconductor device having a projection on a nitride III-V compound semiconductor base body, comprising:
a buried semiconductor layer made of Znx Mg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury a portion around the projection.
According to the tenth aspect of the invention, there is provided a method for manufacturing a semiconductor device having a projection on a nitride III-V compound semiconductor base body and including a buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61) which buries a portion around the projection, comprising the steps of:
making the projection; and
growing the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61) to bury the portion around the projection.
According to the eleventh aspect of the invention, there is provided a method for manufacturing a semiconductor device having a projection on a nitride III-V compound semiconductor base body and including a buried semiconductor layer made of (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) which buries a portion around the projection, comprising the steps of:
making the projection; and
growing the buried semiconductor layer made of (Al1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury the portion around the projection.
According to the twelfth aspect of the invention, there is provided a method for manufacturing a semiconductor device having a projection on a nitride III-V compound semiconductor base body and including a buried semiconductor layer made of ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) which buries a portion around the projection, comprising the steps of:
making the projection; and
growing the buried semiconductor layer made of ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) to bury the portion around the projection.
In the present invention, all of the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), buried semiconductor layer made of (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) and buried semiconductor layer made of Znx Mg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) have the [111] orientation. For growth of these buried semiconductor layers, metal organic chemical vapor deposition (MOCVD) and molecular epitaxy (MBE) are usable. However, in case of selectively growing a buried semiconductor layer on opposite sides of the ridge-shaped stripe or around the projection, metal organic chemical vapor deposition is preferably used. When metal organic chemical vapor deposition is used for the growth, the growth temperature is typically set at 600xc2x0 C. through 900xc2x0 C. for the buried semiconductor layer of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), 500xc2x0 C. through 800xc2x0 C. for the buried semiconductor layer of (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61) and 300xc2x0 C. through 600xc2x0 C. for the buried semiconductor layer of ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, (0xe2x89xa6yxe2x89xa61)). Especially when a semiconductor laser is manufactured, if an InGaN material is used as the material of the active layer, the growth temperature of the buried semiconductor layer is preferably higher than the growth temperature of the active layer for minimizing thermal deterioration of the active layer.
In the present invention, from the standpoint of simplifying the manufacturing process of a semiconductor laser or a semiconductor device and manufacturing it easier, the buried semiconductor layer is preferably grown selectively on opposite sides of the ridge-shaped stripe or around the projection. However, selective growth is not indispensable. That is, it is also possible to make the ridge-shaped stripe or the projection, then grow the buried semiconductor layer on the entire substrate surface so as to cover the ridge-shaped stripe or the projection, and thereafter remove a part of the buried semiconductor layer from above the ridge-shaped stripe or the projection by etching, for example.
In the present invention, the nitride III-V compound semiconductor includes at least one kind of group III element selected from the group consisting of Ga, A1, In, B and T1, and group V elements which include at least N and may further include As or P under certain conditions. Specific examples of nitride III-V compound semiconductor are GaN, A1GaN, A1N, GaInN, A1GaInN, InN, and so on.
According to the semiconductor laser and its manufacturing method having the above-summarized configuration, since opposite sides of the ridge-shaped stripe are buried with the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa6 1) or ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61), heat dissipation from the ridge portion is promoted, and this minimizes deterioration of the active layer and elongates the lifetime of the semiconductor laser.
Additionally, since the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa6 1, 0xe2x89xa6yxe2x89xa61) or ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) absorbs light emitted from the active layer, it forms a loss-guided semiconductor laser capable of stabilizing transverse modes, alleviate higher mode oscillation during high output power, and removing kinks in optical output-electric current curve. Therefore, the stripe width need not be so thin, and the laser can be manufactured easily.
Especially when using metal organic chemical vapor deposition for growth of the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa6 1, 0xe2x89xa6yxe2x89xa61) or ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61), selective growth is possible, and the semiconductor laser can be manufactured easily.
Moreover, by burying the buried semiconductor layer at a lower growth temperature than the growth temperature of the active layer, thermal deterioration of the active layer can be prevented, and a semiconductor laser having a long lifetime can be manufactured.
According to the semiconductor device and its manufacturing method having the above-summarized configuration according to the invention, since the portion around the projection is buried with the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), (A1x Ga1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) or ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61), in the case where the projection becomes a heat generating source, heat dissipation from the ridge portion is promoted, and this minimizes deterioration of the device and elongates the lifetime of the semiconductor device.
Especially when using metal organic chemical vapor deposition for growth of the buried semiconductor layer made of A1xGa1-xAs (0xe2x89xa6xc3x97xe2x89xa61), (A1xGa1-x)yIn1-yP (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61) or ZnxMg1-xSySe1-y (0xe2x89xa6xc3x97xe2x89xa61, 0xe2x89xa6yxe2x89xa61), selective growth is possible, and the semiconductor device can be manufactured easily.
The above, and other, objects, features and advantage of the present invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.